Until recently, no efficient method of removing material from a polycrystalline diamond film was known. See, for instance, the article by W. van Enckevort in Physics World, August 1992, pp. 22-23.
Very recently, such methods were discovered. One approach involves providing for intimate contact at elevated temperature between the diamond film and a solid metal (e.g., Mn, Fe, Ni, Ti) body or powder. See, for instance, S. Jin et al., Diamond and Related Materials, Vol. 2, pp. 1038-1042, S. Jin et al., Applied Physics Letters, Vol. 60 (16), pp. 1948-1950, and U.S. patent application Ser. No. 07/822,470, filed Jan. 17, 1992. Another approach involves contacting, at elevator temperature, the diamond film with a molten rare earth metal (e.g., Y, La, Ce). See, for instance, S. Jin et al., Nature, Vol. 362, Apr. 29, 1993, pp. 822-824, and U.S. patent application Ser. No. 07/908,130, filed Jul. 2, 1992. U.S. Pat. No. 5,328,550, filed Oct. 2, 1992, discloses use of a molten rare metal alloy to effect the material removal at lower temperature, and U.S. patent application Ser. No. 08/038,370, filed Mar. 29, 1993, discloses a technique for selective material removal from the surface of polycrystalline diamond film produce, e.g., a region of lenticular shape. All the above methods are believed to involve diffusion of carbon atoms into the hot metal, the "etchant". The above cited commonly owned U.S. applications are incorporated herein by reference.
Polycrystalline diamond (PCD) film is typically produced by chemical vapor deposition on a substrate. It is frequently observed that the resulting PCD film ("wafer") is not of constant thickness and/or is not flat. Observed variations are frequently as large as .+-.5% over the water, with the central region of the wafer typically having maximum thickness. For many technological applications of PCD bodies it is typically required that the bodies be of a predetermined thickness and/or be flat, within relatively narrow limits. For instance, use of thin PCD bodies as heat spreaders in laser/optical fiber packages requires that the thickness and flatness be closely controlled. However, provision of flat PCD bodies of predetermined thickness is at best difficult if the starting product (namely, the PCD film on the wafer) has curvature and/or has substantial thickness variation. Thus, a method material removal from PCD film that can be used to substantially eliminate curvature and/or thickness variations over a relatively large area (typically tens of square centimeters) would be of considerable interest. This application discloses such a method.
Known diffusional methods of material removal cannot be applied efficiently to the solution of the above described problem since, in most cases, they result in uniform removal over the contacted surface. The method of the '370 application does not readily lend itself to non-uniform material removal over a relatively large region. Of course, conventional methods (e.g., polishing) would be unacceptably time consuming and costly, and would allow treatment of at most a few wafers at a time.